Flexible sigmoidoscopy screening for colorectal cancer in average-risk subjects: a community-based pilot project

Flexible sigmoidoscopy screening for colorectal cancer in average-risk subjects: a community-based pilot project

John K Olynyk, Sina Aquilia, David R Fletcher and Jim A Dickinson

©MJA1996; 165: 74-76.

This article has been cited in Sladden MJ, Ward JE. Australian general practitioners' views and use of colorectal cancer screening tests. MJA 1999; 170: 110-113

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Abstract - Introduction - Methods - Subjects - Data management - Acceptability survey - Results - Subject recruitment - Screening results - Reasons for non-compliance with screening - Discussion - Acknowledgements - References - Author's Details

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Abstract Objective: To test a pilot screening program for colorectal cancer.
Design: Subjects, chosen at random and recruited by mail, were examined by flexible sigmoidoscopy.
Participants and setting: Normal-risk, asymptomatic men and women aged 55-59 years recruited from the community, July to December, 1995.
Main outcome measures: Number of polyps detected and cancers diagnosed, and compliance with screening.
Results: Letters of invitation were sent to 3500 subjects; of these, 2881 were eligible for inclusion in the study and 342 (12%) consented to participate. A further 3.5% of non-compliant subjects attended the screening program after a telephone survey assessing reasons for non-attendance. Common reasons for non-attendance were a lack of interest (30%) or a lack of time, mainly due to work commitments (28%). A third of subjects had polyps and 46% of these were adenomas. Three subjects were found to have adenocarcinoma: in two the cancer was confined to a polyp and treated with polypectomy, and one subject underwent anterior resection (overall prevalence of cancer, 0.9%). The median depth of insertion achieved with flexible sigmoidoscopy was 55 cm (range, 25-100 cm). Median pain level (on a scale of 0 = no pain to 10 = worst pain imaginable) was 2 (range, 0-8.5), and 99% of the subjects would have the test again if required.
Conclusions: Flexible sigmoidoscopy was well tolerated and had an acceptable detection rate of adenomatous polyps and early cancer. Subject compliance emerged as a major issue which requires further evaluation to maximise participation in future programs.

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MJA 1996; 165: 74-76

Introduction

C olorectal cancer is the commonest cancer affecting both sexes and isnow the second-commonest cause of cancer-related death in both men and women. ¹ Several studies have shown that screening asymptomatic populations may reduce mortality from colon cancer by up to 30%, ^2-4 and recently the World Health Organization recommended screening of asymptomatic subjects beginning at age 50. ⁵ However, in Australia there are no uniformly agreed methods for screening asymptomatic subjects for colorectal cancer. ⁶ Factors such as screening efficacy, cost, subject compliance and strategies employed to evaluate positive results all influence the choice of screening test.

Faecal occult blood testing for colo rectal cancer is relatively cheap, but is limited by a high rate of false positive results and poor sensitivity. ^7-9 A recent report also suggests that up to half the mortality reduction observed with faecal occult blood screening may be due to chance selection for colonoscopy. ¹⁰ Flexible sigmoidoscopy has been proposed as an alternative screening test. It is more expensive but would prevent more cancer deaths than faecal occult blood testing alone. ^8,11

Apart from determining the best screening methods, rates of compliance with screening programs range widely (8%-80%). ^8,12 These issues, together with implications for health service resource allocation, have prompted recommendations for pilot programs to determine the efficacy of screening and compliance rates before more generalised screening is introduced. ^6,8,13 The Western Australian Department of Health provided funds for such a pilot project at Fremantle Hospital.

Thus, we were able to conduct a pilot community-based flexible sigmoid oscopy screening program, between July and December 1995, for colorectal cancer in normal-risk asymptomatic individuals, and in this setting determine (i) yield of screening, and (ii) subject compliance with screening and factors which influence compliance.

Methods A flexible sigmoidoscopy facility dedicated to colorectal cancer screening was established at Fremantle Hospital. All procedures were performed on an outpatient basis after informed written consent. No sedation was used. After administration of a phosphate enema, procedures were performed either by a qualified gastroenterologist, or a general practitioner who was undergoing supervised training in flexible sigmoidoscopy. An Olympus TI100 colonoscope (Olympus Optical, Japan) was used, allowing insertion up to 100 cm. Biopsies were taken from polyps seen during the procedure. Subjects with biopsy-proven adenomas were advised to have a follow-up colonoscopy. A computer-generated report was issued to all subjects after the procedure, with instructions to return to their general practitioner for ongoing care. The study was approved by the Ethics Committee of Fremantle Hospital.

Subjects We recruited male and female subjects aged 55 to 59 years of age using a computerised database derived from the Western Australian Electoral Commission. Letters were sent to 3500 randomly selected subjects inviting their participation. Exclusion criteria (apart from age less than 55 or greater than 59 years) were: symptoms of recent alteration in bowel habit, constipation, diarrhoea, or passage of blood with bowel motions; previous history of colonic polyps or colorectal cancer; and family history of colorectal cancer.

A telephone survey of 200 subjects who did not respond to the initial letter showed that the reason for non-attendance in 14% of these subjects was that they met the exclusion criteria.

Data management All data were recorded on a customised database from which reports were generated. We recorded basic demographic data, presence or absence of exclusion criteria, operator information, date of procedure, adequacy of bowel preparation, insertion depth, polyp data (number, size, pedunculated or sessile, biopsy report and date), and follow-up advice.

Acceptability survey After the procedure, 77 consecutive subjects filled in a brief questionnaire, which included a standard 10-cm linear analogue pain scale. They marked a 10-cm line (labelled "0 = no pain" and "10 = worst pain imaginable") at a point which corresponded to their level of pain.

Results

Subject recruitment One hundred and fifty letters were returned, indicating that the subject was no longer resident at the mailing address. As 14% of non-attending subjects were found by the telephone survey to meet exclusion criteria, we estimate there were 2881 eligible subjects. Of those, 342 (12%) consented to participate in the study. There were 200 men and 142 women participants; 95% were born in Australia.

Screening results Findings at flexible sigmoidoscopy are summarised in Box 1. The median depth of insertion achieved was 55 cm (range, 25-100 cm; 70% of subjects had at least 50 cm of bowel examined by flexible sigmoidoscopy. Thirty-five subjects (10%) were incompletely prepared with one enema and required a repeat bowel preparation before the procedure. Thirty-five per cent of subjects had polyps -- 46% of these polyps were adenomas, the remainder being hyperplastic or metaplastic polyps. The median adenoma size was 4 mm (range, 1-60 mm). Nineteen of the adenomatous polyps (5.6%) were at least 1 cm in size. One subject with a 6-cm sessile villous adenoma underwent anterior resection. Three subjects were found to have adenocarcinoma -- in two the cancer was confined to a polyp and treated with polypectomy, while the third required anterior resection for a cancer detected at follow-up colonoscopy. The overall prevalence of cancer in this group of subjects was 0.9%.

The median pain score attributed to the procedure was 2 (range, 0-8.5). Seventy-six (99%) of these subjects would have the test again if required. Most subjects found the procedure interesting (they were able to watch on a video screen) and worthwhile.

Reasons for non-compliance with screening The commonest reasons given for non-compliance were a lack of interest (30%) or a lack of time, mainly due to work commitments (28%) (Box 2). Interestingly, 16% of subjects who did not attend stated that they had either discussed the issue of bowel cancer screening to their satisfaction with their local general practitioner or had been screened for bowel cancer. Seventeen (8%) of the 200 subjects who did not attend as a result of the initial mail-out indicated that they would like to participate as a direct result of the telephone interview and were offered appointments; seven (3.5%) of these subjects have since attended for screening.

Discussion The cancers detected by flexible sigmoidoscopy in our study were early cancers, but our three cases represent a detection rate of 8.8 cancers per 1000 asymptomatic subjects aged 55-59. Western Australian data for this age group predict an annual incidence of about 1 per 1000. ¹

Our yield of polyps at least 1 cm in size (5.6%) is consistent with the previously reported prevalence of polyps in persons aged 55-59 ¹⁴ and in asymptomatic Australian men of mean age 66 (3.8%). ¹⁵ However, the depth of insertion and number of polyps found in our study are both greater than those reported in several recent studies of flexible sigmoidoscopy: their average depth of insertion ranged from 30 to 50 cm ^16-19 and polyp yield ranged from 1% to 4%. ^18,19

There is little doubt that population response to screening will be a major determinant of the utility of flexible sigmoidoscopy as a screening tool for colo rectal cancer. The reasons given for non-compliance are similar to those reported for non-attendance in faecal occult blood screening programs. ²⁰ Although the initial response in the pilot program was 12%, the survey of non-compliant subjects demonstrated a significant opportunity for improvement. An additional 3.5% of subjects could immediately be given an appointment at the time of the telephone survey of non-compliant subjects, bringing the compliance rate to 15.5%. Of the remaining reasons determined for non-compliance, most could be addressed by better education of subjects, and rescheduling of screening times to suit the work practices of potential candidates. It remains to be seen how much this would actually improve screening rates.

Sixteen per cent of non-compliant subjects reported that they had either been screened for colorectal cancer or had discussed the issue to their satisfaction with their local general practitioner. This may reflect the growing public and general practitioner awareness of colon cancer screening; this has recently been reported from South Australia. ²¹ There is no doubt that the highest possible compliance should be aimed for, but in a society where currently only 41% of subjects with rectal bleeding seek medical attention ²² it would seem that much education needs to occur to facilitate this process.

We have reported the first Australian pilot study of flexible sigmoidoscopy screening of asymptomatic subjects aged 55-59 years in which a high yield of adenomatous polyps and early cancers was found. The procedure was well tolerated. Subject compliance emerged as a major issue which requires further evaluation in order to maximise participation in future programs. This study strongly supports a more broad-scale evaluation of flexible sigmoidoscopy screening of asymptomatic subjects for colorectal cancer and polyps.

Acknowledgements We wish to thank Dr Digby Cullen, Mr Graham Cullingford and the Gastroenterology Departments of Fremantle Hospital, Sir Charles Gairdner Hospital and Royal Perth Hospital; Dr Andrew Penman, formerly Chief Health Officer of the Health Department of Western Australia, and the Fremantle Division of General Practice, for their support of this study.

References

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(Received 6 Feb, accepted 22 Apr 1996)

For editorial comment, see Solomon, page 68; see also Macrae, page 102.

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Authors' details

University Department of Medicine and Department of Gastroenterology, Fremantle Hospital, Fremantle, WA.
John K Olynyk , FRACP, MD, Senior Lecturer and Head of Department of Gastroenterology.
Sina Aquilia , BA(Psych), Research Assistant.
University Department of Surgery and Department of Gastroenterology, Fremantle Hospital, Fremantle, WA.
David R Fletcher , FRACS, MD, Professor of Surgery, Head of Department of Surgery.
University Department of General Practice, Fremantle Hospital, Fremantle, WA.
Jim A Dickinson , FRACGP, PhD, Professor of General Practice.
Reprints: Dr J Olynyk, University Department of Medicine, Fremantle Hospital, PO Box 480, Fremantle, WA 6160.
E-mail: jolynyk AT uniwa.uwa.edu.au < URL: http://www.mja.com.au/> © 1996 Medical Journal of Australia.